Resin compositions used in the filed of electric and electronic appliances are required to have superior flame retardancy for their safety; therefore, extensive research and development has been made for “flame-retardant resins”. Polycarbonate type resins have excellent heat resistance, excellent electrical properties, etc. and accordingly they are being actively developed as a resin material for flame-retardant resin composition.
Currently, resin compositions used in the filed of electric and electronic appliances are required to have even higher flame retardancy and it is being attempted to further improve the flame retardancy of polycarbonate type resins by adding thereto various flame retardants.
Bromined compounds, phosphorus compounds, etc. have been used as conventional flame retardants. In recent years, however, it has been required to achieve flame retardancy without using any halogen atom. In such a situation, it is being attempted to improve the flame retardancy of polycarbonate type resins by compounding thereinto a small amount of inorganic particles.
In, for example, JP-A-2004-010825 (Patent Literature 1) is disclosed a flame-retardant resin composition wherein inorganic particles of silica or the like are compounded into an aromatic polycarbonate. Specifically explaining, consideration is made on the shape of the inorganic particles compounded, in order to improve the flame retardancy of aromatic polycarbonate.
Also, JP-A-2001-152030 (Patent Literature 2) discloses a flame-retardant material which contains particles of 10 to 100 nm in particle size obtained by grinding an inorganic porous material loaded with a flame retardant. Exactly, it is a flame-retardant resin material obtained by firing an inorganic material such as porous glass, silicon oxide, aluminum oxide or the like to form a porous material, loading thereon an additive (a flame retardant) selected from metals, metal salts and inorganic compounds, then passing the additive-loaded porous material (particles) and a resin (e.g. a polycarbonate or a polypropylene) through a twin-screw extruder to conduct fine pulverization and mixing simultaneously. It is described in the Patent Literature 2 that, in the flame-retardant material, the additive is dispersed well and thereby flame retardancy is achieved.
Patent Literature 1: JP-A-2004-010825
Patent Literature 2: JP-A-2001-152030